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Shell Programming: The Complete Documentation

• This category contains 14 Papers
• The last paper was added on 2007-03-26 (YYYY-MM-DD)

"Cannot execute /bin/bash: Permission denied" - solved!

Published on April 2000, by Ben Okopnik, ©Specialized Systems Consultants.

Just a few minutes before sitting down to write this article, I managed to fix a problem that has been the bane of my existence for the last two weeks. Since it is a problem that I have often seen mentioned in the Linux Gazette, usually phrased in a manner that shows the writer to be standing on a chair with a noose around his neck and typing with his toes, I've decided to share it with other readers, hopefully saving them wear and tear on good rope. This may also serve as a good guide to troubleshooting software problems in general. Be aware, though, that a login problem could involve _any_ of the areas described - what fixed my particular machine may not be the solution for yours.

Advanced Bash-Scripting Guide

Published on June 21, 2003, by Mendel Cooper, ©Linux Documentation Project.

This tutorial assumes no previous knowledge of scripting or programming, but progresses rapidly toward an intermediate/advanced level of instruction . . . all the while sneaking in little snippets of UNIX wisdom and lore. It serves as a textbook, a manual for self-study, and a reference and source of knowledge on shell scripting techniques. The exercises and heavily-commented examples invite active reader participation, under the premise that the only way to really learn scripting is to write scripts.

BASH Programming - Introduction HOW-TO

Published on June 21, 2003, by Mike G mikkey, ©Linux Documentation Project.

This article intends to help you to start programming basic-intermediate shell scripts. It does not intend to be an advanced document (see the title). I am NOT an expert nor guru shell programmer. I decided to write this because I'll learn a lot and it might be useful to other people. Any feedback will be apreciated, specially in the patch form :)

Bash Prompt HOWTO

Published on August 28, 2001, by Giles Orr, ©Linux Documentation Project.

Creating and controlling terminal and xterm prompts is discussed, including incorporating standard escape sequences to give username, current working directory, time, etc. Further suggestions are made on how to modify xterm title bars, use external functions to provide prompt information, and how to use ANSI colours.

Command-line interactive programs in UNIX shell-scripts

Published on 2005-06-21, by Mikhail E. Zakharov, Mikhail E. Zakharov.

Like it or not, but sooner or later you realize that you'll have to write shell-scripts to administer UNIX. And among these scripts there certainly will be those to cooperate with interactive applications such as telnet, ftp, su, password, ssh. But it means the end of the admin's quiet life because while dealing with interactive programs one often come across numerous hidden traps which doesn't usually happen with ordinary sh-scripts. Though fortunately or may be not, but most of these problems generally turn up within first five minutes of the work under the script. The symptoms typically look like that author can't pass the authentication from the script.

Deep, Dark Secrets of Bash (The)

Published on July 2000, by Ben Okopnik, ©Specialized Systems Consultants.

Deep within the bash man page lurk terrible things, not to be approached by the timid or the inexperienced... Beware, Pilgrim: the last incautious spelunker into these mysterious regions was found, weeks later, muttering some sort of strange incantations that sounded like "nullglob", "dotglob", and "MAILPATH='/usr/spool/mail/bfox?"You have mail":~/shell-mail?"$_ has mail!"'" (He was immediately hired by an Unnamed Company in Silicon Valley for an unstated (but huge) salary... but that's beside the point.)

Encrypting Shell Scripts

Published on 2005-01-13, by Duane Dunston, ©Guardian Digital, Inc..

Do you have scripts that contain sensitive information like passwords and you pretty much depend on file permissions to keep it secure? If so, then that type of security is good provided you keep your system secure and some user doesn't have a "ps -ef" loop running in an attempt to capture that sensitive info (though some applications mask passwords in "ps" output). There is a program called "shc" that can be used to add an extra layer of security to those shell scripts. SHC will encrypt shell scripts using RC4 and make an executable binary out of the shell script and run it as a normal shell script. This utility is great for programs that require a password to either encrypt, decrypt, or require a password that can be passed to a command line argument.

Introduction to Shell Scripting

Published on June 21, 2003, by Ben Okopnik, ©Specialized Systems Consultants.

Last month, we took a look at some basics of creating a shell script, as well as a few of the underlying mechanisms that make it all work. This time around, we'll see how loops and conditional execution let us direct program flow in scripts, as well as looking at a few good shell-writing practices.

Introduction to Shell Scripting (2)

Published on June 2000, by Ben Okopnik, ©Specialized Systems Consultants.

Last month, we looked at loops and conditional execution. This time around, we'll look at a few of the simpler "external" tools (i.e., GNU utilities) that are commonly used in shell scripts. Something to keep in mind as you read this article: the tools available to you as a script writer, as you might have guessed from the above quote, are arranged in a rough sort of a "power hierarchy". It's important to remember this - if you find yourself continually being frustrated by the limitations of a specific tool, it may not have enough "juice" to do the job.

Introduction to Shell Scripting (3)

Published on September 2000, by Ben Okopnik, ©Specialized Systems Consultants.

At this point in the series, we're getting pretty close to what I consider the upper limit of basic shell scripting; there are still a few

Safely Creating Temporary Files in Shell Scripts

Published on 2004-02-10, by Stefan Nordhausen, ©Guardian Digital, Inc..

This paper discusses how a programmer can write shell scripts that securely create temporary files in world/group writable directories. After explaining why it is important to be careful with temporary files I give some hints on how to identify and fix vulnerable shell scripts. This paper concentrates on how things are done. I intentionally leave out lots of gory details in order to make this document shorter and easier to understand for people that just want to write secure code with as little extra effort as possible.

Shell Programming

Published on September 2001, by Katja and Guido Socher, ©LinuxFocus.

In this article we explain how to write little shell scripts and give many examples.

Shell Programming

Published on September 2001, by Katja and Guido Socher, ©LinuxFocus.

In this article we explain how to write little shell scripts and give many examples.

Shell Scripting Tutorial (Linux)

Published on 2002, by Vivek G. Gite, ©FreeOS.com (I) Pvt. Ltd..

This tutorial is designed for beginners who wish to learn the basics of shell scripting/programming plus introduction to power tools such as awk, sed, etc. It is not help or manual for the shell; while reading this tutorial you can find manual quite useful (type man bash at $ prompt to see manual pages). Manual contains all necessary information you need, but it won't have that much examples, which makes idea more clear. For this reason, this tutorial contains examples rather than all the features of shell.